已知x-3y=0,求x平方减2xy+y平方分之2x+y乘以(x-y)的值

有
X-3Y=0
X=3Y
(2X+Y)(X-Y)/(X²-2XY+Y²)
=(2X+Y)(X-Y)/(X-Y)²
=(2X+Y)/(X-Y)
=(2*3Y+Y)/(3Y-Y)
=7Y/2Y
=7/2

已知x-3y=0,则x/y=3; 设x/y=u 那么 u=3
(x-y)(2x+y)/[x^-2xy+y^2)]=[2x^2-xy-y^2]/[x^-2xy+y^2)] 分子分母同除以y^2得
=(2u^2-u-1)/(u^2-2u+1)=14/4=7/2

不知道题目是不是这样
(2x+y)(x-y)/（x^2-2xy+y^2)
因为x-3y=0所以x=3y代入得
（18y^2-3y^2-y^2)/(9y^2-6y^2+y^2)
=14y^2/4y^2
=14/4
=7/2

X-3Y=0
X=3Y
(2X+Y)(X-Y)/(X²-2XY+Y²)
=(2X+Y)(X-Y)/(X-Y)²
=(2X+Y)/(X-Y)
=(2*3Y+Y)/(3Y-Y)
=7Y/2Y
=7/2

x-3y=0
x=3y
原式=(2x+y)(x-y)/(x-y)²
=(2x+y)/(x-y)
=(6y+y)/(3y-y)
=7y/2y
=7/2

是计算题的话这样做X-3Y=0X=3Y(2X+Y)(X-Y)/(X